1. Field of the Invention
The invention relates in general to a transparent window, and more particular, to a floating window suitable for use in a flatbed scanner.
2. Related Art of the Invention
In the recent years, the great advancement of computer and the highly developed Internet and multi-media techniques allow extracting an image pattern from a digital camera (DC) directly. On the other hand, the image input process of other relative documents or pictures require an optical scanner to obtain an analog image therefrom. The analog image is then converted into a digital signal to be output. The users can thus perform display, recognition (OCR), edit, storage and output operation of the image file in a computer or an electronic product.
According to the input method, the optical scanner can be categorized into palm scanner, sheet feed scanner, drum scanner and flatbed scanner. As the flatbed scanner has a more stable image scanning quality and functions of document (film and projection film) reflection and transmission, plus an additional automatic document feeder (ADF) can be used to continuously scan a whole stack of documents with the same size; therefore, the flatbed scanner becomes one of the most commonly used optical scanners currently.
The flatbed scanner incorporates a transparent flat panel, for example, a piece of glass or transparent plastic, mounted on a top lid of thereof for disposing the document to be scanned. Using a belt driving apparatus and the bearing positioning mechanism, the optical scan module, that is, the chassis, inside of the flatbed scanner is linearly directed, such that the internal linear optical sensor of the chassis such as the charge-coupled device (CCD) or the contact image sensor (CIS) is driven to scan the surface of the document, so as to obtain an analog image signal. The analog image signal is then converted into a digital image signal to be output.
Referring to FIGS. 1A and 1B, the top lid and the transparent flat panel of a conventional flatbed scanner before assembly are schematically illustrated. In FIG. 1A, an opening 12 is formed at a center of the top lid 10 of the flatbed scanner. A transparent flat panel 20 is typically disposed on a bottom wall of the top lid 10. The surface area of the transparent flat panel 20 is slightly larger than the size of the opening 12. Therefore, the opening 12 is completely covered with the transparent flat panel 20. An adhesive region 22 is formed surrounding the opening 12 on the bottom wall of the top lid 10 to attach the transparent flat panel 20. As shown in FIG. 1B, the central region of the transparent flat panel 20 is positioned and exposed over the opening 12 where the document to be scanned is disposed.
During the assembly of the chassis of the flatbed scanner, an adjusting toll is used to adjust the focus of the chassis. For the assembly process of the transparent flat panel, as mentioned above, the transparent flat panel is directly adhered on the bottom wall of the top lid without any correction operation. Therefore, when the document is scanned by the chassis, once the top lid or the base is deformed or the internal base of the flatbed scanner is not sufficiently planar, the distance between the transparent flat panel and the chassis is not constant. Consequently, deviation between the scanned image and the actual image of the document is caused. Especially for the scanning system of the contact image sensor, or for the high-resolution or low-depth optical scan module, the distance between the transparent flat panel and the optical scan module often seriously affects the image scan quality of the flatbed scanner.